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Compendium June 2011 (Vol 33, No 6)

Clinical Snapshot: Abdominal Distention in a Dog

by Christina M. Bove, DVM

    Case Presentation

    A 13-year-old, male, neutered golden retriever mix presented in the evening with a distended, painful abdomen. The dog had a 2-day history of lethargy and had vomited once the evening before evaluation. On the morning of the day of presentation, the dog had been inappetent and the abdomen had started to distend. The abdominal swelling became progressively worse during the day, and the dog had not wanted to get up that evening. The medical history included arthritis, which had been treated on an as-needed basis with an NSAID. The dog had not received this medication recently. Physical examination revealed pyrexia (105.3°F [40.7°C]; normal range: 100.5°F to 102.5°F [38.1°C to 39.2°C]), pale mucous membranes with a prolonged capillary refill time of 2.5 seconds, moderately increased respiratory effort and tachypnea (respiratory rate: 40 breaths/min;normal range: 15 to 30 breaths/min), and an auscultable cardiac arrhythmia (heart rate: 140 bpm;normal range: 60 to 120 bpm) that consisted of a regular rhythm with short periods of tachycardia, with fair synchronous pulses. The patient was laterally recumbent with a severely distended abdomen and appeared depressed and uncomfortable.

    1. Given the history and clinical signs, what are the major diagnostic differentials?

    2. A right lateral abdominal radiograph was obtained (FIGURE A). What abnormalities are seen? What is your diagnosis?

    3. What are the major causes of this condition?

    Answers and Explanations

    1. The major diagnostic differentials for the distended abdomen in this dog were gastric dilatation–volvulus, hemoabdomen, a ruptured gastrointestinal tract causing pneumoperitoneum, uroperitoneum, and ascites due to right-sided heart failure, hepatic failure, or protein-losing nephropathy/enteropathy.

    2. Abdominal radiography revealed severe pneumoperitoneum (FIGURE B). The abdominal side of the diaphragm (straight arrows), cranial margin of the liver (curved arrows), and cranial pole of one of the kidneys (arrowhead), as well as the serosal margins of all the abdominal viscera, are visible. The stomach is small and not overly distended. The large amount of gas is consistent with rupture of a large hollow viscus such as the stomach. Pneumoperitoneum is defined as the presence of gas or air in the peritoneal cavity that is not contained in a hollow viscus.1 It usually suggests serious intraabdominal disease, and immediate surgical intervention is often needed.2

    Pneumoperitoneum can generally be diagnosed on lateral and dorsoventral radiographs if there is a substantial amount of gas present, as in this case.1,3 Postural or positional radiography may be needed for diagnosis when there is only a small amount of air.3,4 This is because on conventional radiographs taken with a vertically directed x-ray beam, air bubbles are small and irregular in shape, and larger bubbles can be superimposed over viscera.3 Pneumoperitoneum with a small amount of air is best seen using horizontal-beam radiography in combination with nonstandard patient positioning, such as recumbent left lateral and inverted lateral projections.1,3,4 When a horizontally directed x-ray beam is used, the patient is best positioned on an angle between left lateral and ventrodorsal recumbency, with the cranial portion of the abdomen slightly elevated from the table.3 This allows the gas to rise along the right side of the abdominal wall to the highest point, which is usually caudal to the diaphragm and adjacent to the liver lobes.3,4 Right lateral recumbency is not recommended because gas bubbles will rise to the left side and may be confused with gas in the gastric fundus.3

    3.Major causes of pneumoperitoneum are postoperative, traumatic, and spontaneous,1 with the most common cause in small animals being recent celiotomy with air trapped during closure and absorbed by the peritoneum.5,6 After intraabdominal procedures, small amounts of free gas can be detected radiographically for up to 25 days in dogs and 30 days in humans.2 Pneumoperitoneum beyond 30 days postoperatively signifies an underlying pathologic condition.1 Traumatic causes of pneumoperitoneum include vehicular impact, gunshot wounds, and animal bite wounds or deep lacerations that penetrate the abdominal wall, allowing free gas to enter the peritoneum from outside the body.1,5 Spontaneous pneumoperitoneum can result from gastrointestinal tract perforation due to neoplasia (lymphosarcoma, leiomyosarcoma), steroid and/or NSAID administration, gastric dilatation–volvulus, and complications associated with percutaneous endoscopically placed gastrostomy tubes.1,4 Other causes include urinary bladder rupture, splenic necrosis,1 and infection with gas-producing organisms.4 There is also a report of idiopathic pneumoperitoneum in a dog.4 In humans, this condition is characterized by free gas in the abdomen without evidence of peritonitis, a perforated gastrointestinal tract, or penetrating abdominal wounds.

    ***

    The cause of the pneumoperitoneum in this dog could not be determined because the owners declined surgical exploration and elected humane euthanasia. Perimortem abdominocentesis confirmed a large amount of abdominal gas. A necropsy was also declined. There was no sign of penetrating wounds or recent abdominal surgery. Thus, this dog was categorized as likely having either spontaneous or idiopathic pneumoperitoneum. Based on the dog’s signalment, clinical signs, and large amount of gas, gastric perforation due to neoplasia or gastric dilatation–volvulus was suspected.

    References

    1. Saunders WB, Tobias KM. Pneumoperitoneum in dogs and cats: 39 cases (1983-2002). JAVMA 2003;223(4):462-468.

    2. Mehl ML, Sequin B, Noordin RW, et al. Idiopathic pneumoperitoneum in a dog. JAAHA 200;37(6):549-551.

    3. Mahaffey MB, Barber DL. The peritoneal space. In: Thrall DE, ed. Textbook of Veterinary Diagnostic Radiography. 4th ed. Philadelphia: WB Saunders; 2002:516-539.

    4. Thariani-Mizra TF, Williams J, Jaffe M. What is your diagnosis? Pneumoperitoneum with mild abdominal effusion, caused by rupture of the stomach. JAVMA 1998;213(10):1403-1404.

    5. Strom AM, Pacchiana P. What is your diagnosis? Pneumoperitoneum. JAVMA 2007;230(4):505-506.

    6. Probst CW, Stickle RL, Bartlett PC. Duration of pneumoperitoneum in the dog. Am J Vet Res 1986;47:176-178.

    References »

    NEXT: Equine Recurrent Uveitis: Classification, Etiology, and Pathogenesis

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